The conventional terrestrial digital TV transmission systems widely employ a single-frequency network architecture, namely, TV towers at different locations transmit the same signal at the same frequency simultaneously.
The disadvantage is that the number of the transmit towers and the transmit power are subject to certain constraints. For urban topography, there will be many shadow areas for indoor reception, and for rural topography, the coverage range will be limited in some extent. On the other hand, the conventional digital TV transmission system is for one-way broadcast. This one-way broadcast mode transmits a fixed number of video programs with limited bandwidth, without taking into account the specific service needs of users, e.g., two-way services such as video on-demand, information customization, games, etc.